Liverpool full-back Alberto Moreno has been ruled out of this weekend's meeting with Everton and is doubtful for his side's busy festive programme.
The 25-year-old, who has resurrected his Reds career by featuring 18 times so far this term, damaged a tendon in his left ankle during the 7-0 victory against Spartak Moscow.
Klopp is still unsure how long the Spaniard is facing on the sidelines, with further tests scheduled to assess the full scale of the damage.
However, should the tendons be damaged it will likely mean an absence of around six weeks, potentially ruling Moreno out for the remainder of December and the majority of January.
Asked for a fitness update, manager Jurgen Klopp told reporters: "I'm not sure. We need to have further assessment. So far it could be everything. I cannot say much about it.
"It's a very rare thing. So far the specialists aren't sure. Not Everton, but if it's in a week or so or a little bit longer we have to wait for that. There's a little damage around the tendons."
Klopp also hinted in his pre-match press conference ahead of Sunday's visit of Everton that skipper Jordan Henderson will start in central midfield after being rested last time out.
